Atrial Septal Defect

History

Paroxysmal nocturnal dyspnea, Orthopnea, and shortness of breath on exertion

These symptoms occur with late development of heart failure.

Arrhythmia

Although uncommon in pediatric patients, evidence has shown patients with ASD have a considerable rate of sinus arrhythmia.
Furthermore, untreated ASD can cause atrial dilatation and atrial arrhythmia in later life (around the age of 40) [2]

Cyanosis (both peripheral and central)

If the ASD remains untreated for a long time, the right ventricle hypertrophies, causing pulmonary hypertension. Once this occurs, the usual shunt through the ASD reverses, and blood flows from right to left. This is called Eisenmenger's syndrome.

Examination

Fact

Explanation

Mild left precordial bulge on inspection of the precordium

Left parasternal lift due to right ventricular dilatation. [1] This occurs with increased precordial activity and suggests cardiac enlargement. Such bulges can often best be appreciated by having the child lay supine with the examiner looking up from the child’s foot end.

Left parasternal heave

The right atrium hypertrophies and the heart is pushed towards the precordium; thus the left parasternal heave can be palpated.

A fixed and widely split second heart sound

Normally, the duration of right ventricular ejection varies with respiration, with inspiration increased right ventricular volume delays the closure of the pulmonary valve, increasing the split of second heart sound. With an ASD, right ventricular diastolic volume is constantly increased and the ejection time is prolonged throughout all phases of respiration. [2]

An ejection systolic murmur best heard in the left sternal edge.

The left to right shunt increases the right ventricular output. This causes increased blood flow through the right ventricular outflow tract resulting in a flow murmur.

With the development of right sided heart failure the right ventricle and the right atrium fails to adapt and function as an effective pump. This results in back flow of blood causing increased JVP. Hepatic congestion causes tender hepatomegaly.

Clinical features of other co-existing valvular anomalies may be detected. Eg: mitral valve abnormalities, and aortic valve abnormalities. [3]

The finding of such co-existent valvular anomalies would be in favour of Ostium primum ASD (OP-ASD), as opposed to Ostium secundum ASD (OS-ASD); however neither can be confidently confirmed clinically.

References

BROWN J H and FONG E W, MD. Case Based Pediatrics For Medical Students and Residents. Department of Pediatrics, University of Hawaii John A. Burns School of Medicine. March 2003

Differential Diagnoses

This is also a malformation of the common wall between the superior vena cava (SVC) and the right-sided pulmonary veins and results in an interatrial communication. [1]

ASD sinus venosus

When an associated ASD is present with partial anomalous pulmonary venous return, it is generally of the sinus venosus type, or less frequently, of the secundum type. [2]

Atrioventricular septal defects

Deficiency or the absence of the atrio-ventricular septum. [3]

Partial Anomalous Pulmonary Venous Circulation

When an ASD is detected by echocardiography, one must always search for associated partial anomalous pulmonary venous return. The history, physical signs, and electrocardiographic and CXR findings are indistinguishable from those of an isolated OS ASD.

Investigations - for Diagnosis

Fact

Explanation

Chest X-ray

Enlarged right ventricle and atrium is seen depending on the size of the ASD. The lateral view demonstrates the enlargement of the right ventricle better than the antero-posterior view [1]. Enlarged pulmonary vessels and increased pulmonary vascular markings may be seen due to increased pulmonary blood flow. In some patients, the CXR may be completely normal. [2,3]

Electrocardiogram (EKG)

Left axis deviation is seen in OP-ASD; whereas right axis deviation and partial right bundle branch block are seen in OS-ASD. The RSR' pattern in V1 and in other right ventricular leads is also detected in ASD.

2D Echo-cardiogram

2D Echo cardiogram, when combined with color Doppler, demonstrates the defect in the interatrial septum. 2D Echo-cardiogram demonstrates the features of right ventricular overload, including increased end-diastolic right ventricular dimensions.
This will enable to detect other co-existing anomalies as well.

Diagnostic cardiac catheterization

Although invasive and has a significant radiation exposure risk cardiac catheterisation confirms the presence of the defect and allows measurement of the shunt ratio and pulmonary pressure and resistance.

Investigations - Fitness for Management

Fact

Explanation

Chest X Ray (CXR)

Features of heart failure will be evident on CXR. Eg: Pulmonary congestion, Kerley B-lines, Cardiomegaly, Fluid in the fissures.

Cardiac catheterization

This helps in detecting the degree of pulmonary hypertension, and the direction of blood flow through the ASD and aids in deciding whether or not to close the shunt. Severe pulmonary hypertension and shunt reversal are usually contraindications for shunt closure. [1]